一种实用的动态模糊度表示方法

文章分析了动态模糊逻辑理论中动态模糊数据的构成，根据实际需要，将动态模糊数据分离成模糊数据和动态数据进行表示，提出了一种新的动态度的表示方法，并给出了动态度的近似计算方法。     

动态模糊Petri网模型及其应用研究

以模糊Petri网的基本定义，动态模糊集和动态模糊逻辑为基础，讨论了动态模糊Petri网的基本模型，建立了动态模糊Petri网与模糊Petri网之间的映射关系和转移算法，解决了与动态模糊知识的动态模糊Petri网表示相关的几个问题，最后给出了动态模糊Petri网中动态模糊性的计算方法和相应的推理方法。     

无线传感器网络动态协同任务分配机制

以无线传感器网络单目标追踪为背景，提出了一种基于仲裁的动态联盟协同任务分配机制，简化了现有动态联盟的形成机制，提高了动态联盟的结盟成功率，并加入了盟员更新机制，实现了动态任务分配，从而在降低能量消耗的同时提高了网络性能．在仿真中，将基于仲裁的动态联盟协同任务分配机制与现有的基于案例推理的动态联盟机制进行比较，验证了基于仲裁的动态联盟机制在能耗和追踪性能方面的优势．     

一种基于遗传算法的自适应动态模糊系统的设计与实现

在我们研究的领域中，动态模糊对象是普遍存在的．因此由这些动态模糊对象组成的系统即为动态模糊系统，这类系统具有较强的自学能力和自适应能力，能随环境的变化而变化，本文借助动态模糊集和遗传算法对动态模糊系统进行研究，给出了一种动态模糊自适应系统，并进行了实例分析，实验结果表明该系统是有效的．     

压力传感器动态性能分析及改进

传感器的动态性能是否符合要求对测试结果的准确性至关重要。通过压阻式压力传感器的动态校准实验数据，建立其动态数学模型，并由此求出动态特性指标，最后设计出动态补偿数字滤波器，明显提高了传感器动态响应的快速性和展宽了工作频带。     

递归复合型模糊神经网络结构研究

针对一类能够有效引入过程先验知识的复合型模糊神经网络，研究了其动态结构． 通过对复合型模糊神经网络的函数网络的第二层引入动态递归环节，使其具有动态映射能力 ，实现了对动态系统的良好响应．本文采用了动态非线性模型对其进行仿真研究，结果 表明，对于处理动态非线性系统，此动态复合模糊神经网络较之静态网络在收敛速度、预测 精度和网络规模等方面都有较大的改善．     

DyTrust:一种P2P系统中基于时间帧的动态信任模型

针对现有的信任模型对节点行为改变的动态适应能力和对反馈信息的有效聚合能力支持不足，提出一个基于时间帧的动态信任模型DyTrust，使用时间帧标示出经验和推荐的时间特性，引入近期信任、长期信任、累积滥用信任和反馈可信度4个参数来计算节点信任度，并通过反馈控制机制动态调节上述参数，提高了信任模型的动态适应能力．仿真实验表明，与已有的信任模型相比，DyTrust具有更好的动态适应能力和反馈信息有效聚合能力，能够有效处理动态恶意节点策略性的行为改变和不诚实反馈对系统的攻击．     

一种基于免疫原理的动态入侵检测模型

根据生物免疫原理，提出了一个新的动态入侵检测模型，并对模型的体系结构作了详细的描述，包括自体的演化、动态耐受和动态免疫记忆过程的数学描述，同时提出基于LRU算法的记忆检测器动态降职机制。实验表明该模型具有更好的动态性和有效性。     

基于QoS的动态服务组合研究

传统的动态服务组合在可靠性和效率方面存在缺陷，随着Web服务的不断进步和发展，如何克服这些缺陷显得日益重要。着重从如何提高动态服务组合的执行效率和改善服务组合结构入手，进行基于QoS的动态服务组合研究，以期达到提高动态服务组合效率的目的。     

动态系统的一致同余安全

研究动态系统的安全问题．针对动态系统运行时间配置的可变特性，引入了动态系统的进程代数模型和复杂动态系统概念，定义了动态系统的一致安全性质和一致同余安全性质．基于观察同余等价，构造了一类一致同余安全模型．本文证明，动态系统的安全性质是一致安全性质，而对于复杂动态系统，其安全性质是一致同余安全性质．     

Model identification using tie line power and frequency measurements

The identification of dynamic models which relate power and frequency deviations on a tie line of a power system is investigated. The identification problem is posed and three identification algorithms are presented which produce least squares models with different structural properties. Model order is determined by applying residual and system structure tests to a sequence of models of increasing order. These tests indicate the model order for both equivalent realizations and predictive models. Equivalent realizations are identified on one data set and then their performance as a dynamic equivalent is evaluated on a second data set. These equivalent realizations are also used to predict frequency in an iterative frequency prediction algorithm. Predictive models are also identified and their performance as frequency predictors is evaluated using a direct prediction algorithm. The identification of dynamic equivalents provides information about the structural properties of power systems. The use of dynamic equivalents and predictive models for frequency prediction indicates the tradeoff in accuracy vs the prediction interval which can be obtained using these least squares algorithms and the measurement device presently available.     

样条函数在系统频域分析中的应用——系统动态响应实用分析方法之二（对数频率特性法）

自动控制系统的动态性能的分析方法包括时域分析法,频域分析法,及稳定性判据。具体的分析法有微分方程,传递函数,方框图,伯德图,奈奎斯特图和根轨迹等。对数频率特性法是频域分析中应用较为广泛的一种。文章从自动控制系统的动态性能分析方法入手,着重探讨了样条函数在系统频域分析中的应用,并举例加以说明。     

样条函数在系统频域分析中的应用——系统动态响应实用分析方法之二(对数频率特性法)

自动控制系统的动态性能的分析方法包括时域分析法,频域分析法,及稳定性判据.具体的分析法有微分方程,传递函数,方框图,伯德图,奈奎斯特图和根轨迹等.对数频率特性法是频域分析中应用较为广泛的一种.文章从自动控制系统的动态性能分析方法入手,着重探讨了样条函数在系统频域分析中的应用,并举例加以说明.     

The role of actual modal-contributions versus frequency to optimize the structure

In modal frequency response analysis, the dynamic analyst is often faced with the structure’s dynamic behavior, the modal contributions included, over a frequency window rather than at a single frequency. Therefore a new method in modal frequency response analysis has been developed for computing both complex modal-contributions and real, actual modal-contributions over a frequency range. Contributions from normal modes to displacement, velocity, or acceleration of a set of selected evaluation points (grid-component combinations) are considered. The focus lies on identifying the major actual-contributions from normal modes and the frequency range they are active in. The method is valid for all branches of mechanical engineering. With the thorough knowledge of the dominant modal-contributions to the physical motion response of relevant structure locations and the modal contributions’ frequency history, the traditional design process can substantially be enhanced. It is worthwhile to notice that by the use of the presented procedure the dynamic analyst may find innovative redesigns which the automatic structural optimizers are not able to find. Examples are given to demonstrate the application, the strength of the coupling between modes, the influence of base and force excitation on the modal contributions and, finally, some recommendations on how to reduce undesired structural responses.     

Dynamic stability of viscoelastic nanotubes conveying pulsating magnetic nanoflow under magnetic field

In this study, dynamic stability analysis of viscoelastic carbon nanotubes (CNTs) conveying pulsating magnetic nanoflow subjected to a longitudinal magnetic field is investigated. Based on Hamilton’s principle, the governing equations as well as boundary conditions, are extracted. The dynamic instability region and pulsation frequency of the CNTs are obtained through both the Galerkin technique and the Bolotin method. The effects of the nonlocal parameter gather with strain gradient parameter, Knudsen number, magnetic field, mass fluid ratio, fluid velocity, tension, gravity, viscoelastic characteristic of materials and boundary conditions on the dynamic instability of system are deliberated. The results indicate that increase in the pulsation frequency is caused by the decrease of nonlocal parameter and the increase of strain gradient parameter. Besides, it is revealed that by increasing Knudsen number the pulsation frequency decreases. Furthermore, the dynamic instability region and pulsation frequency of CNT can be enhanced due to the magnetic field effects.

     

基于神经网络的速度传感器幅频特性改进

为了降低磁电式振动速度传感器的下限测量频率,以实现超低频振动速度测量,提出改进其幅频特性的函数连接型人工神经网络(FLANN)方法。该方法以磁电式振动速度传感器动态试验数据为基础,通过FLANN训练来确定传感器动态补偿网络,以改善它的幅频特性。介绍了原理和FLANN权值调整的算法,给出用FLANN建立的磁电式振动速度传感器动态补偿网络的数学模型。结果表明:这种幅频特性的改进方法具有精度高、鲁棒性好,并能在线修正等优点,在工程测试领域有重要的实用价值。     

Time history dynamic analysis of structures using filter banks and wavelet transforms

Dynamic analysis of structures is achieved by wavelet transforms and filter banks. The method reduces the computational burden of the large-scale dynamic analysis. A time history analysis is carried out for a seismic analysis. To reduce the computational work, fast wavelet transform is used. To compute fast wavelet transforms, the Mallat and the Shensa algorithms are used. These two methods are used for wavelet theory together with filter banks. The low and high pass filters are used for the decomposition of accelerogram ground acceleration into two parts. The first part contains the low frequency of the record, and the other contains the high frequency of the record. The low frequency content is the most important part; therefore this part of the record is used for dynamic analysis. A number of structures are analysed and the results are compared with dynamic analysis using the original earthquake record.     

提高边缘吞吐量的软频率复用改进方案研究

对于固定软频率复用算法在小区边缘用户分布不均匀时,无法动态地分配频率资源而造成系统整体频谱资源浪费的问题,提出一种动态软频率复用算法。在此算法中,以边缘用户在相邻小区间的分布为依据,将小区边缘频段进一步划分,将频率资源动态地分配给用户,分布较多边缘用户的小区将会分配到较多的频率资源,而分布较少边缘用户的小区就会分配到较少的资源。通过仿真可知,与固定软频率复用算法相比,动态软频率复用算法在几乎不影响中心用户吞吐量的同时提高了边缘用户的吞吐量。因此,动态软频率复用算法能够在小区边缘用户分布不均匀时,有效解决系统整体频谱资源浪费的问题。     

Transmission of dynamic biochemical signals in the shallow microfluidic channel: nonlinear modulation of the pulsatile flow

A controlled quantitative loading of dynamic biochemical signals on cells in vitro is essential for cell dynamic analysis. Microfluidics provides the potential for reproducing and controlling spatio-temporal biochemical signals through the various microfluidic channels. Herein we investigate the transmission characteristics of dynamic biochemical signals in pulsatile flows by analytically solving the convection–diffusion equation for the time-dependent Taylor–Aris dispersion with perturbation method. We prove that the transmission of dynamic biochemical signals in pulsatile flows is subject to the two correlate effects: low-pass filtering and nonlinear amplitude–frequency modulation. These two effects are systematically characterized and the influence factors are studied, including the biochemical signal frequency, the pulsatile flow frequency, the transmission distance and the average pulsatile flow rate. We concluded that the balance of multiple factors should be taken into account for better loading biochemical signals on cells cultured in the microfluidic channel.     

Study of human–seat interface pressure distribution under vertical vibration

The influence of whole-body vertical vibration on the dynamic human–seat interface pressure is investigated using a flexible grid of pressure sensors. The ischium pressure and the overall pressure distribution at the human–seat interface are evaluated as functions of the magnitude and frequency of vibration excitation, and seated posture and height. The dynamic pressure at the seat surface is measured under sinusoidal vertical vibration of different magnitudes in the 1–10 Hz frequency range. Two methods based on ischium pressure and ischium force are proposed to study the influence of seat height, posture and characteristics of vibration. The results of the study reveal that the amplitude of dynamic pressure component increases with an increase in the excitation amplitude in almost entire frequency range considered in this study. The dynamic components of both the ischium pressure and the ischium force reveal peaks in the 4 to 5 Hz frequency band, the range of primary resonant frequency of the seated human body in the vertical mode. The mean values of the dynamic ischium pressure and the ischium force remain constant, irrespective of the excitation frequency and amplitude. The magnitudes of mean pressure and force at the human–seat interface, however, are dependent upon the seat height and the subject's posture. The inter-subject variability of the static ischium pressure and effective contact area are presented as functions of the subject weight and subject weight-to-height ratio. It was found that heavy subjects tend to induce low ischium pressure as a result of increased effective contact area.

Relevance to industry

Pressure distribution at the human–seat interface has been found to be an important factor affecting the seating comfort and work efficiency of various workers. The study of human–seat interface pressure distribution under vibration is specifically critical to the comfort, work efficiency and health of vehicle drivers, who are regularly exposed to vibration. The results reported in this paper will be useful to study dynamic response of the interface pressure and design vehicle seats.